Hitchcocks Forum

Hi- please can I have some advice?

I have a 1992 500 bullet classic, which is pretty much as standard. Had a new Mk 1 Concentric about a year ago & ran very well until after a couple of months slumber under a cover during the worst of the winter. I then put on a new Fifties style exhaust & started riding again. After about a week an occasional misfire started which has become progressively worse. Starts very easily but above tickover and when warm the engine hunts about and under load it misses quite badly- the best way to describe it is that it feels like a multi-cylindered engine going onto two or three cylinders instead of four! Very distracting especially in heavy traffic. My daily commute is about 18 miles taking in dual carriageway and town riding at each end. Ive checked: points & timing- clean, gapped properly, timing set up with dial gauge & then checked again by Roadstar in Dover. New condenser, new BR8ES plug, HT lead & ends. Bags of compression. Put on a new coil and the problem vanished- for a day!- then it's started again & is getting progressively worse. Did wonder if it was carb being upset by the new exhaust so put the old pipe back on but no difference. Does anyone have any ideas? Thanks for any suggestions.

I noticed you'd had it put away for a couple of months.. have you refuelled it since, or is it still on the old fuel..? (I'm thinking water or ethanol in the fuel here..).

I had this happen to me once, years ago, on a Honda. I pulled the fuel line off and blew it through back to the tank just to be sure the fuel line wasn't blocked in the tank. It helped.

Hi Exile

I've got through several tank-fulls since then- the problem persists with fresh fuel, which is ordinary unleaded. I've cleaned the fuel filter under the tap and there was virtually no gunge in the bottom of the carb- incidentally the carb did seem quite sooty inside - a thin deposit which was easily wiped off. All the jets are clear. When I did a plug test- ran it on three-quarter throttle for a mile with the engine popping and banging- the plug seemed wet & possibly faintly sooty which makes me think its running a bit rich which is surprising given the less restrictive exhaust. The carb has a K&N type air filter by the way- the standard Hitchcock kit. I'm told they like to run a bit rich and I'd be surprised if the carb set up would affect the running so badly unless it was completely wrongly jetted, which it doesn't seem to be. I must admit it does feel like carburation but the fact that it ran so well for a while after fitting the new coil makes me suspect electrics.

By the description of what's happening, I would suggest a faulty condenser / dirty points might be the culprit.

Just read that you have a BR8ES plug - try a B8ES with no resistor, that might help. Regards, Paul.

Sounds more electrical than carb but you never know, check the main jet is secure and has not loosened off..

Eliminate ignition switch/harness prob by fitting a short length of wire from the batt direct to the coil..

Just as a temporary measure, stop the motor with the decomp. Earth wire engine to batt using croc clips may give improvement and show faulty earth connection..

Suppose timing advance not seized up full retard??

Have you any problems starting the machine? And are you using and petrol additives?

Oop just saw you say she's starting easily enough, so just the question, are you using any additives?

Hi chaps
Thanks for all the replies.
Firstly, she starts very readily- I never have to use choke. No additives- just plain old unleaded. Did a top end rebuild about 4000 miles ago & all well with the valves- rebore, new piston & rings. My gut feeling is that it's the points- I'll have another go at cleaning them & try another condenser but I'll also have the carb off & check the seals between carb, manifold & head. Advance / retard seems to move freely & I replaced the bush on the shaft a while back (hmm- I also fitted a grease nipple to the shaft housing like the early ones had- wonder if there's grease on the points?). I'll try Gwilly's wiring tips as well.

For the price... New points instead of just cleaning them?